1. Field of the Invention
The present invention is directed to a method for forming a dry metal halide salt which will form a clear colorless solution upon dissolving in water. More particularly, this invention is concerned with preventing the formation of an insoluble flocculent material upon dissolving a dry metal halide salt in water.
2. Description of the Prior Art
Clear, high density brines are used in oil well completions and workovers. They are also used as oil well packer fluids. Packer fluids are the fluids which are left in the annular space between the tubing and casing of oil wells. The primary purpose of these fluids is to balance the pressure in the well so as to prevent a well "blow out" without losing the fluid to the formation, and without damaging the formation as is done when solids-laden fluids are used. The densities required by these brines are determined by the well pressures and depths.
Brine is typically defined as water which is nearly saturated with salts. Oil well brines are usually prepared by blending different amounts and types of salt solutions to get the required density and clarity at the lowest cost. Such brines must be clear, that is, free of solids or solids-forming materials.
Calcium bromide has traditionally been available as a liquid, that is, commercial sale of calcium bromide has usually been as a brine. At the well site the density of the brine could be decreased by adding more water. Shipping costs over large distances were higher than necessary since much of the brine was water. By shipping dry metal halide salts shipping costs can be minimized. The salt can then be dissolved in water by the driller at the well site to form brine of the required density.
Metal halides used in completion fluids are made in an aqueous medium by reaction of a metal base such as CaO, Ca(OH).sub.2, ZnO and the like with HCl, HBr or Br.sub.2 with a reducing agent such as methanol. The dry metal halides are made by evaporating the water from these initial solutions. However, it was discovered that upon redissolving the dry salt, an insoluble flocculent material was formed. This insoluble flocculent material is undesirable for oil well completion fluids because it may damage the well formation. The cause of the floc may have originated in the brine manufacturing process. Alternatively, floc-causing impurities may have been acquired by the solution during shipping, storage or handling.